1. Technical Field
The present invention relates generally to compositions comprising antigenic and/or immunogenic combinations of Mycobacterium tuberculosis antigens and their use in the diagnosis, treatment, and prevention of tuberculosis.
2. Description of the Related Art
Tuberculosis is a chronic infectious disease caused by infection with Mycobacterium tuberculosis and other Mycobacterium species. It is a major disease in developing countries, as well as an increasing problem in developed areas of the world, with several million new cases each year. Although infection may be asymptomatic for a considerable period of time, the disease is most commonly manifested as an acute inflammation of the lungs, resulting in fever and a nonproductive cough. If untreated, serious complications and death typically result.
Although tuberculosis can generally be controlled using extended antibiotic therapy, such treatment is not sufficient to prevent the spread of the disease. Infected individuals may be asymptomatic, but contagious, for some time. In addition, although compliance with the treatment regimen is critical, patient behavior is difficult to monitor. Some patients do not complete the course of treatment, which can lead to ineffective treatment and the development of drug resistance.
In order to control the spread of tuberculosis, effective vaccination and accurate early diagnosis of the disease are critical. Currently, vaccination with live bacteria is the most widely used method for inducing protective immunity. The most common Mycobacterium employed for this purpose is Bacillus Calmette-Guérin (BCG), an avirulent strain of Mycobacterium bovis. However, the safety and efficacy of BCG is a source of controversy and some countries, such as the United States, do not vaccinate the general public with this agent.
Diagnosis of tuberculosis is commonly achieved using a skin test, which involves intradermal exposure to tuberculin PPD (protein-purified derivative). Antigen-specific T cell responses result in measurable induration at the injection site by 48-72 hours after injection, which indicates exposure to mycobacterial antigens. Sensitivity and specificity have, however, been problematic, and individuals vaccinated with BCG cannot be distinguished from infected individuals.
Accordingly, there is a need for improved reagents and methods for diagnosing, preventing and treating tuberculosis. The present invention fulfills these needs and offers other related advantages.